diff --git a/include/mitsuba/core/plugin.h b/include/mitsuba/core/plugin.h
index 7bb8f045..28cd1fcd 100644
--- a/include/mitsuba/core/plugin.h
+++ b/include/mitsuba/core/plugin.h
@@ -23,8 +23,6 @@
 
 MTS_NAMESPACE_BEGIN
 
-class Utility;
-
 /**
  * \brief Abstract plugin class -- represents loadable configurable objects
  * and utilities.
diff --git a/include/mitsuba/core/util.h b/include/mitsuba/core/util.h
index 9cc55cab..f022b04f 100644
--- a/include/mitsuba/core/util.h
+++ b/include/mitsuba/core/util.h
@@ -21,7 +21,6 @@
 
 MTS_NAMESPACE_BEGIN
 
-class Random;
 // -----------------------------------------------------------------------
 //  Miscellaneous
 // -----------------------------------------------------------------------
diff --git a/include/mitsuba/render/film.h b/include/mitsuba/render/film.h
index e0482876..65bc9255 100644
--- a/include/mitsuba/render/film.h
+++ b/include/mitsuba/render/film.h
@@ -27,8 +27,6 @@ namespace fs = boost::filesystem;
 
 MTS_NAMESPACE_BEGIN
 
-class Bitmap;
-
 /** \brief Abstract Film base class - used to store samples
  * generated by the Integrator.
  */
diff --git a/include/mitsuba/render/fwd.h b/include/mitsuba/render/fwd.h
index 7cac1010..5c40444a 100644
--- a/include/mitsuba/render/fwd.h
+++ b/include/mitsuba/render/fwd.h
@@ -74,6 +74,7 @@ class Texture;
 struct TriAccel;
 struct TriAccel4;
 class TriMesh;
+class Utility;
 class VolumeDataSource;
 struct VPL;
 
diff --git a/include/mitsuba/render/renderproc.h b/include/mitsuba/render/renderproc.h
index 0b151132..82ff9ed7 100644
--- a/include/mitsuba/render/renderproc.h
+++ b/include/mitsuba/render/renderproc.h
@@ -25,8 +25,6 @@
 
 MTS_NAMESPACE_BEGIN
 
-class RenderJob;
-
 /**
  * Parallel process for rendering with sampling-based integrators. Splits
  * an image into square pixel regions, which can be processed independently.
diff --git a/include/mitsuba/render/renderqueue.h b/include/mitsuba/render/renderqueue.h
index f127f31b..73bbbb3a 100644
--- a/include/mitsuba/render/renderqueue.h
+++ b/include/mitsuba/render/renderqueue.h
@@ -24,8 +24,6 @@
 
 MTS_NAMESPACE_BEGIN
 
-class RenderJob;
-
 /** 
  * Abstract render listener - can be used to react to 
  * progress messages (e.g. in a GUI)